#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
    int n = 0,m = 0,x = 0,y = 0;
    cin >> n >> m >> x >> y;
    x += 1,y += 1;
    vector<vector<long long>> dp(n+2,vector<long long>(m+2,0));//dp[i][j]表示从(0,0)到(i,j)的所有路径数
    dp[0][1] = 1;
    for(int i = 1;i < n+2;++i)
    {
        for(int j = 1;j < m+2;++j)
        {
            if(i != x && j != y && abs(i-x) + abs(j-y) == 3 || (i == x && j == y)){
                dp[i][j] = 0;
            }
            else{
                dp[i][j] = dp[i-1][j] + dp[i][j-1];
            }
        }
    }
    cout << dp[n+1][m+1];
    return 0;
}